Cobalt oxide (Co₃O₄) is one of the most widely used pigments in ceramics, known for its ability to generate a wide range of blue hues. This oxide is highly potent, meaning that even small amounts can produce intense and deep colors. Its chemical and thermal stability makes it an ideal choice for use in glazes and engobes over the entire temperature range, from low to high firing.
In transparent glazes, cobalt oxide produces a vivid, uniform blue, while in opaque or textured glazes it can generate complex visual effects, such as speckled patterns or color gradients. In combination with other oxides, it can produce secondary colors, such as bluish greens when mixed with copper oxide or deep purples when combined with manganese.
Interesting Fact
Cobalt oxide has been used in ceramics since the 8th century, when it was discovered that it could produce intense blues in Chinese porcelains. Later, its use spread to Delft pottery in the Netherlands and to Spanish earthenware.
Helpful Tip
Due to its high potency, start with very low proportions of cobalt oxide (about 0.5%) and adjust according to the desired shade. Wear gloves and a mask when handling, as the powder can be irritating. Test on small pieces to understand how it interacts with your glazes and firing conditions.
